A group of French researchers on Friday claimed they have found a way to prevent the WannaCry ransomware from permanently blocking the Windows files of users who refuse to pay the money demanded by the hackers. With the largest number of computers having been hacked last Friday, the week-long deadline to save the files has almost run out, Reuters reported.

The group of researchers, who are based out of different cities, includes security expert Adrien Guinet, Matthieu Suiche, an internationally known hacker, and Benjamin Delpy, who works at the Banque de France. The team collaborated on how to unlock the encryption key that blocks the files, and have named their code “wanawiki”.

The researchers, however, added that “wanawiki” will only work on computers that have not been rebooted since being infected and if the owners use it before the files are permanently locked. The system is expected to work on all Windows Operating Systems that have been affected by WannaCry.

The WannaCry cyber attack is believed to have been developed by using a leaked code from the United States National Security Agency. Researchers from various cyber security firms said the hackers made a self-spreading malware by exploiting a piece of NSA code. The code, known as “Eternal Blue”, was stolen and released on April 14 by a group called Shadow Brokers.

Meanwhile, North Korea denied it had anything to do with the attack, Reuters added. “Relating to the cyber attack, linking it to the Democratic People’s Republic of Korea is ridiculous,” the country’s Deputy United Nation Ambassador Kim In Ryong told a media conference on Friday. “Whenever something strange happens, it is the stereotype way of the United States and the hostile forces that kick off noisy anti-DPRK campaign deliberately linking with DPRK.”

Earlier, security companies Symantec and Kaspersky Lab had said the WannaCry software had a code that was identified in the programmes used by North Korea cybergang Lazarus Group. “This is the best clue we have seen to date as to the origins of WannaCry,” Kaspersky Lab researcher Kurt Baumgartner had said.